Method and apparatus for electrical precipitation of suspended particles from gases



Sept. 9. 1924. 1,507,687

. W. A. SCHMIDT METHOD AND APPARATUS FOR ELECTRICAL PRECIPITATION OF SUSPENDED PARTICLES FROM GASES Filed Dec. 15 1920 Fig 7 59.3.

a 13 F'i Q4 /0 U a I as 3 o \83 I F a 34 l/ I V 1v zzvron 38 1g 1/ {2 .7 h/alfel% Schmidt a I 634% lQn/m' u 7 ATTORNEY 40 A such uneven distribution .of the ions there is Patented Sept. 9, 1924.

UNITED STATES 1,507,687 PATENT OFFICE. A

WALTER A. SCHMIDT, 015 .LOS ANGELES, CALIFORNIA, ASSIGNO'R TO INTERNATIONAL CALIFORNIA.

METHOD AND APPARATUS FOR ELECTRICAL PRECIPITATION PARTICLES FROM GASES.

.PRECIPITATICII COMPANY, or LOS ANGELES, CALIFORNIA, A CORPORATION or OF SUSPENDED Application filed December 15, 1920. Serial No. 430,891.

To. all whom it may concern;-

Beit known that I, WALTER A. SCHMIDT, a citizen of the United States, residing at Los Angeles, in the county of Los Angeles and State of California, have invented a new and useful Method and Apparatus for Electrical Precipitation of Suspended Particles from Gases, of which the following is a specification.

This invention-relates to precipitation of suspended material, such as dust and-fume, from gases by electrical action. In such operation as usually carried out the gases to be treated are passed between electrodes maintained at high potential difference, certain of said electrodes being of such natureas to facilitate discharge of electricity into the gases and the action of the electrical 'field causes the suspended particles to be collected on the electrodes.

It has been found that the operation of apparatus of this character is in some cases seriously interfered with by 'reason of the presence of ions in the gases supplied to the electrical precipitating apparatus. This is particularly the case where the gases are received from furnaces in which the gases have been brought into contact with flames, or with bodies at high temperature, for example, in electric furnaces- In such cases there are generally large numbers of ions present in the gases and these ions are generally not uniformly distributed in the gases, some parts of thegases having rela- 'tively large numbers of ions-while other parts of the gases may be comparatively free from ions, -and,- moreover, negative ions, or, in some cases, positive ions, may be preponderantly present in certain portions of the gases and not In others. Owing to considerable variation in the operation of electrical precipitating apparatus due, for

example, to fluctuations in resistance of the gaseous dielectric by reason of variations 301i the ions in different portions of the gases,

it being understood that the greater the ionization the lower will be the electrical resistance .of the gases. Such excessive and variant ionization of the gases is not only objectionable its direct results but tends .to increase the difficulty by cumulative action of the ionization on account of the I rapidly movlng ions tending to produce further ionization by collision with the gaseous molecules, thus. increasing further the ionizat on, and correspondingly decreasing the res stance at parts which are already unduly ion zed, with the result that fluctuations or varlat-lons in resistance of the ases tend to become accentuated and to still further interfere with maintenance of the desired electrical conditions in the precipitator.

W th a gas of a given conductivity, it is possible to adjust the potential difference in an electrical precipitator so as to effect satisfactory precipitation Without breaking down thegaseous dielectric but it is apparent that .with gases fluctuating in resistance from time to time and from place to place 1n the gases, it is not possible to maintam at all times the operating potential difference best adapted to maximum precipitation on account of the liability to breaking down of the gaseous dielectric at parts Where excessive ionization is presented.

The main object of the present invention is to provide for deionization or discharge of the gases to a sufiicient extent to ensure eflective operation of the electrical precipitating apparatus. This object is attained, according to my present invention, b subjectingthe gases to the action of an e ectrostatic field produced between electrodes maintained at suflicient potential difference to cause translation or movement .of the ions to such electrodes, with resultant removal of the ions'from the gases, to a greater or less extent; the 'substantiallyor partially deionized gases then passing to the electrical precipitating apparatus.

The accompanying drawing illustrates apparatus suitable-forcarrying out my invention, and referring thereto Fig. 1 is a horizontal section of one form of such an apparatus;

Fig. 2 is a transverse section on line 2-2 in Fig. 1;

Fig. 3 1s a transverse section on in Fig. 1;-

Fig. 4 is a vertical, section of another form;:

Figs. 5 to 7 are diagrams showing modifications of the current connections.

In Figs. 1 and 2 I have illustrated my invention as applied in connection with a gas receiving flue or chamber 1., extending horizontally and conducting the gas through an electrical precipitator b. In said flue or chamber and in advance of such electrical precipitator I provide deionizing means 01 comprising electrodes 3 and 4 maintained at high potential difference, said electrodes consisting, for example, of, parallel vertical plates or screens of conducting material, such as metal, extending parallel to the di rection of the gas flow. Electrodes 4 are grounded, for example, by connection to the walls of the flue 1, which may be of metal or otherwise constructed so as to be conducting, and the opposing electrodes 3 are insulated, being mounted, for example, by frame 5 on insulators 6, and are connected by wire 7 to a source of high electrical potential, for example, to a high tension alternating current circuit 8 energized from a low tension alternating current circuit 9 by a step-up transformer 10, a rectifier 11 being provided in said high tension circuit connections operating in synchronism with the alternating circuit to deliver rectified or unidirectional electrical current to the electrodes 3, such rectifier having a grounded connection 12 for completing the circuit.

If required, potential controlling means, such as a resistance 13, may be provided in the connection from the high tension circuit to the electrodes 3. By the above described means, or other suitable apparatus, sufficiently high potential difference is maintained between the electrodes 3 and 4 to generate stron electrostatic fields between the opposing e ectrpdes. ing all of extended area and free from points or edges, a purely electrostatic field is pro duced and substantially no electrical discharge takes place from the members 3 and 4. V I

The electrical precipitating apparatus 6 may be of any usual or suitable construction, comprisin for example, collectin electrodes 15 ormed as ounded vertica plates of relatively exten ed area and discharge electrodes 16 formed aswires, rods or other conducting members of relatively small area mounted opposite the collecting electrodes and supported b an insulated'frame 17 which is connected y wire 18 to a suitable source of unidirectional high potential current, for exam Is, to the circuit 8 leading to the rectifier a ove referred to, a resistance 20 being interposed, if required, for controlling the potential.

The operation of this form of tion' is as follows:

The gases to be treated are assumed to be delivered to flue or chamber 1 from an electric furnace, blast furnace, smelting furnace, or other apparatus producing gases my inven- The electrodes becontaining suspended material and also containing ionsin large quantity and in nonuniform distribution. Such gases pass between the opposing electrode members 3 and 4 of'the deionizing means and are subjected to the action of electrical fields maintained between said electrodes, with the result that the ions in the gases are caused to migrate or to be translated laterally of the direction of gas flow, by the force due to the electrostatic field and are collected or absorbed by the said electrodes. The gases passing to the electrical precipitator are, therefore,

substantially or largely deionized, and the distribution of the ions therein is also more uniform, with the result that operation of the electrical precipitator is rendered more uniform and eflicient and the power. consumption of the electrical precipitator is decreased, resulting in considerably higher electrical efliciency.

The potential difference maintained in the deionizing apparatus may be different from that maintained in the electrical precipitator, for example, it may be considerably higher on account of thefact that the electrodes in the deionizing means are all of extended area and without sharp curvature so that the tendency to electrical discharge 1 is reduced to a minimum and comparatively high potential difference can be maintained between the electrodes of the deionizer without breaking down the dielectric or causing,

excessive discharge. The deionizing means consumes a comparatively small amount of current on account of such lack of discharge, the current consumption being mainly that due to the absorption of the electric charges of the ions present in the gases.

As shown in Fig. 5, the deionizing means a and the electrical precipitator b may be connected to separate high potential supply circuits 21 and 22, each provided with rectifier and energized by a ste -up transformer in the manner above descri ed, or as shown in Fig. 6, the deionizer a and the electrical precipitator b may both be ener lzed by d1- ferences such as are usually maintained in electrical precipitators, it is possible, using alternating current of ordinary frequency (60 cycle), to cause suflicient translation of ions to one or the other of'the electrodes during such half wave of alternation to produce the required deionization.

In applying the invention to a horizontal flue treater the electrodes may be placed transversely of the flue, as indicated at 34 and 35 in Fig. 4, for the grounded and the high tension electrodes, respectively, the high tension electrodes being mounted on an insulated frame 36 and the operation being the same as above described in connection with Figs. 1 to 3, except that the gases pass through instead of between the electrodes. In this case, as in the form shown in Figs. 1 to 3, there may be more or less collection of suspended material as well as the ions on the electrodes of the deionizer and such sus pended material is preferably removed from time to time, or continuously, by shaking, jarring, or any other of the well known means for this purpose.

What I claim is:

. 1. The method of treating independently ionized gases containing suspended particles, which consists in. initially subjecting such gases to the action of a purely electrostatic field having an extended sphere of action and of high intensity sufiicient to largely deiouize the gases and then independently subjecting the gas thus treated separately to the action of an electric discharge.

2. The method of treating independently ionized gases containing suspended particles which consists "in initially subjecting such gases to the action of an electrostatic field of considerable extent doetween opposing electrodes of extendedarea maintained at high potential difference whereby the gases are deionized to the required extent by the action of the electrodes, and then passing the gases through a separate and distinct electric field in which an electrical discharge is produced, "to separate the suspended particles from the gases.

3. The method which consists in initially passing an independently ionized gas containing suspended particles, through an extended electrostatic field, between non-discharging electrode .surfaces of extended area, maintained at high potential diiference to cause translation of ions in the gases to i ing electrode means also of-extended area,

opposing the first named electrode means defining therewith an electric field of considerable extent in the direction of the gas flow, and means for maintaining said electrodes at high potential difi'erence.

5. Apparatus for the treatment of independently ionized gases containing suspended material, comprising electrodes constructed and arranged to produce an initial purely electrostatic field having an extended sphere of action and having substantially no electric discharge when maintained at a high potential difference, a separate and distinct electric precipitator and means for passing the .gas to be treated successively through the sphere of action of said electrodes and the precipitator. V

In testimony whereof I have hereunto subscribed my name this 7th day of December, 1920.

.WALTER A. SCHMIDT. 

